Incretins in Normal Physiology

The roles of insulin and glucagon in the regulation of glucose control are shown below. In the fed state (eg, after a meal), glucose levels increase (hyperglycemia), which triggers an insulin response from the beta cells of the pancreas and reduces glucagon secretion by the alpha cells in the pancreas.^9-11

Insulin decreases plasma glucose levels by^9,10:

• Reducing glucose production from the liver
  
• Increasing glucose uptake in peripheral tissues (eg,muscle and fat)
• Decreasing glucagon secretion from the pancreas

In the fasting state (eg, after an overnight fast or between meals), plasma glucose levels decrease and, consequently, glucagon is secreted by the alpha cells in the pancreas,whereas insulin production is decreased.^9,12 Glucagon increases plasma glucose levels by stimulating glucose production from the liver.^9,12